Implement RandR 1.5 support (#2580)

This comes with the intentionally undocumented --disable-randr15 command
line flag and disable-randr15 configuration directive. We will add
documentation before the release if and only if it turns out that users
actually need to use this flag in their setups. Ideally, nobody would
need to use the flag and everything would just keep working, but it’s
better to be safe than sorry.

fixes #1799

testcases/inject_randr1.5.c

@@ -294,7 +294,6 @@ static void read_server_x11_packet_cb(EV_P_ ev_io *w, int revents) {
 
             if (sequence == connstate->getmonitors) {
                 printf("RRGetMonitors reply!\n");
-                xcb_randr_get_monitors_reply_t *reply = packet;
                 if (injected_reply != NULL) {
                     printf("injecting reply\n");
                     ((generic_x11_reply_t *)injected_reply)->sequence = sequence;

testcases/t/201-config-parser.t

@@ -467,6 +467,8 @@ my $expected_all_tokens = "ERROR: CONFIG: Expected one of these tokens: <end>, '
         force_focus_wrapping
         force_xinerama
         force-xinerama
+        disable_randr15
+        disable-randr15
         workspace_auto_back_and_forth
         fake_outputs
         fake-outputs

testcases/t/533-randr15.t

@@ -66,7 +66,42 @@ close($outfh);
 
 my $pid = launch_with_config($config, inject_randr15 => $outname);
 
-cmd 'nop';
+my $tree = i3->get_tree->recv;
+my @outputs = map { $_->{name} } @{$tree->{nodes}};
+is_deeply(\@outputs, [ '__i3', 'DP3' ], 'outputs are __i3 and DP3');
+
+my ($dp3) = grep { $_->{name} eq 'DP3' } @{$tree->{nodes}};
+is_deeply($dp3->{rect}, {
+        width => 3840,
+        height => 2160,
+        x => 0,
+        y => 0,
+    }, 'Output DP3 at 3840x2160+0+0');
+
+exit_gracefully($pid);
+
+################################################################################
+# Verify that adding monitors with RandR 1.5 results in i3 outputs.
+################################################################################
+
+# When inject_randr15 is defined but false, fake-xinerama will be turned off,
+# but inject_randr15 will not actually be used.
+my $pid = launch_with_config($config, inject_randr15 => '');
+
+$tree = i3->get_tree->recv;
+@outputs = map { $_->{name} } @{$tree->{nodes}};
+is_deeply(\@outputs, [ '__i3', 'default' ], 'outputs are __i3 and default');
+
+SKIP: {
+    skip 'xrandr --setmonitor failed (xrandr too old?)', 1 unless
+        system(q|xrandr --setmonitor up2414q 3840/527x2160/296+1280+0 none|) == 0;
+
+    sync_with_i3;
+
+    $tree = i3->get_tree->recv;
+    @outputs = map { $_->{name} } @{$tree->{nodes}};
+    is_deeply(\@outputs, [ '__i3', 'default', 'up2414q' ], 'outputs are __i3, default and up2414q');
+}
 
 exit_gracefully($pid);